Environmental impact of textile barriers

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Examensarbete för Teknologie Kandidatexamen med huvudområde Textilteknologi

2019-06-09 Rapport nr 2019.2.03

Environmental impact of

textile barriers

- A comparative study of coated and laminated textile

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Abstract

This thesis examined how the sustainability of laminated and coated textile barriers can be compared by analysing them through an environmental and functional perspective. This was done by building an evaluation model in which an analysis of the functional performance and an analysis of the

environmental performance was combined and applied on a case study of a laminated and a coated material used for workwear. A Life Cycle Assessment (LCA) was used to evaluate the environmental impact. To evaluate the functional performance a series of material testing was made for tear strength, waterproofness and permeability.

The LCA measured the environmental impact in terms of water use, climate change, and human toxicity. The results showed a similar impact on climate change and water use for both barriers. The assessment of human toxicity showed that the solvent dimethylformamide, used in the coating paste, meant a potential risk for human health. From the material testing it could be stated that the coating performed better in terms of tear resistance and waterproofness, but that the laminate showed more even results and higher breathability.

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Sammanfattning

I den här rapporten undersöktes hur hållbarheten hos laminerade och textila barriärer kan jämföras genom både ett funktionellt och ett miljömässigt perspektiv. Det gjordes genom att bygga en utvärderingsmodell inom vilken en analys av den funktionella prestandan och en analys av den miljömässiga prestandan kombinerades för att appliceras på en fallstudie av ett laminat och en beläggning som används för arbetskläder. En livscykelanalys (LCA) användes för att analysera den miljömässiga prestandan. För att analysera den funktionell prestandan utfördes en serie materialtester i rivstyrka, vattentäthet och permeabilitet.

LCAn mätte miljömässig prestanda genom påverkanskategorierna klimatförändring, vattenanvändning och humantoxicitet. Resultaten visade liknande påverkan avseende klimatförändring och

vattenanvändning för materialen. Utvärdering av påverkan gällande humantoxicitet visade att lösningsmedlet dimetylformamid, som används i beläggningspastan, innebär en risk för människors hälsa. I materialtesterna gav beläggning bättre resultat i rivstyrka och vattentäthet, men laminatet visade en mindre spridning i resultaten och en högre permeabilitet. Efter viss förslitning och tvätt uppvisade materialen dock mer liknande värden.

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Popular abstract

Textiles have always been used as a mean to protect our bodies from wind, water and harmful situations. In many work situations, the use of functional and protective textiles is completely necessary for guaranteeing the safety of the worker. As with many other textiles, the production of functional textiles has a negative impact on the environment. The use of chemicals, water and energy to produce textiles called waterproof breathable fabrics (WPBF) will result in impacts that have effects on ecosystems as well as humans.

The purpose of this study was to compare the sustainability of two types of WPBF used as barriers in workwear: a coating and a laminate. A coated textile barrier is made by applying a viscous paste onto a textile and then dried, while a laminated textile barrier is the adhesion of a thin film, web or

membrane onto the textile. The study aimed to develop and implement an evaluation model for comparing sustainability by combining an analysis of environmental performance with functional performance. In this way, a more nuanced and complex picture of what sustainability of textile barriers means would be made.

The environmental impact was evaluated by using a Life Cycle Assessment (LCA). In an LCA, the potential environmental impact in each step of the product’s life cycle is measured. However, in this study, only the production processes for the materials were included in the LCA. The impacts of the materials in this study were measured in three categories: climate change, water use and human toxicity. For the evaluation of the functional performance, a series of material testing was made for tear strength, waterproofness and breathability.

The results from the LCA showed that the production of the two materials used similar quantities of water, and that the amount of water used was more depending on if the textile was dyed in a

traditional process with several water baths and rinses, or if the dyestuff was added directly into the spindope. The laminate had a larger environmental impact in terms of climate change. The reason for this was probably that the data for the production processes were based on a much smaller production batch for the laminate, which gave it a relatively higher impact per measured unit. For human toxicity, the coated textile had a higher impact due to the use of the solvent dimethylformamide. This solvent evaporates during production and is highly toxic to humans by inhalation.

The coated barrier showed higher values in tear strength and waterproofness, while the laminated barrier had better breathability. After abrasion and washing, the results were more even. This could imply that the materials would have the same functional performance after some time of use.

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Foreword

This report is written as the final thesis in the Bachelor’s program in Textile Engineering at the Swedish School of Textiles. The work has been divided equally between the authors, and has for the most part been done together. The work presented in this report has been conducted at RISE IVF and the Swedish School of Textiles. The laboratory work has been carried out at both places, whereas the LCA-work exclusively has been done at RISE IVF.

We would like to take the opportunity to acknowledge the people who have given us help and support throughout this project. To our supervisors Mats Johansson and Sandra Roos – thank you for your guidance, patience and for sharing your knowledge with us. We feel so lucky to have been assigned this interesting project and been given such competent supervisors. We would also like to thank the staff at the Swedish School of Textiles, RISE IVF and our classmates for all the help and

encouragement. Finally, to our biggest supporters Petter and Hamed, thank you!

List of abbreviations

DMF: Dimethylformamide

DWR: Durable Water Repellent

GWP: Global Warming Potential

LCA: Life Cycle Assessment

LCI: Life Cycle Inventory Analysis

LCIA: Life Cycle Impact Assessment

MVTR: Moisture Vapour Transmission Rate

PES: Polyester

PPE: Personal Protective Equipment

PU: Polyurethane

Ret: Resistance to evaporative heat transfer

SVHC: Substance of Very High Concern

WPBF: Waterproof Breathable Fabrics

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Definitions

Breathability: The ability of a fabric to let water vapour molecules pass through, from the inside to the outside of the fabric.

Cradle-to-gate: An LCA model that include the processes from raw material extraction to finished product at factory gate.

Characterisation factors: These are indicators that reflect the relative contribution to the environmental impact. The collected data is multiplied with the corresponding characterisation factor to get a

quantitative measure of how much impact the product or service has in different impact categories.

Climate change: An impact category expressing the global warming potential of different emissions.

Functional unit: The function of the studied product or service, expressed in quantitative terms. This functional unit serves as basis for the calculations and is the reference to which all other data in the LCA model are related.

Goal and scope: The first phase of the LCA, where it is decided on what product or system to study and what the functional unit will be. The impact categories are also stated here, as well as what processes are being studied.

Human toxicity: An impact category expressing to what degree chemical emissions damage the health of humans.

Hydrophobic: Having no affinity to water (water repellent).

Hydrophilic: Having affinity to water (water absorbent).

Impact categories: Environmental consequences of different environmental loads, for example climate change, toxicity and water use.

LCA: A holistic method where a product or system is studied from a life cycle perspective.

LCI: The second phase of the LCA where the data is collected. The inputs and outputs of the analysed activities are also presented here.

LCIA: The third phase of the LCA, where the information about inputs and outputs from the LCI is quantified into environmental impacts with the help of characterisation factors.

Oleophilic: Having affinity to oil (oil absorbent).

Water consumption: The amount of water that is used in the direct production processes.

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List of figures

Figure 1. The four phases of an LCA as seen in ISO 14040:2006. Figure 2. Schematic illustration of different ways of creating a laminate.

Figure 3. Schematic illustration of the cross section of a coated fabric and a laminated fabric. Figure 4. Microporous barrier structure.

Figure 5. Water vapour passing through a hydrophilic polymer. Figure 6. Dimethylformamide molecule.

Figure 7. Basic outline for the design of the evaluation model.

Figure 8. The methodological framework within the evaluation model. Figure 9. Schematic diagram over the report design.

Figure 10. Illustration of the connection between database used for inventory data, methods

for measuring impact categories and the LCA software SimaPro.

Figure 11. The data handling process, from collection of raw data to calculation of

environmental impact.

Figure 12. General flow chart of the production of the coated and the laminated textile. Figure 13. Flow charts of the material production, from fibre spinning to finished fabric. Figure 14. Illustration of the substances used for creating the coating paste and the

laminated barrier.

Figure 15. An analysis of the climate change for the coated and laminated fabric. Figure 16. Contribution to climate change from each process for the production of the

coating.

Figure 17. Contribution to climate change from each process for the production of the

laminate.

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Figure 21. Mean values of tear strength in warp direction. Figure 22. Mean values of tear strength in weft direction.

Figure 23. Mean values of tear strength in warp direction, before and after washing. Figure 24. Mean values of tear strength in weft direction, before and after washing. Figure 25. Water resistance for the coated and laminated materials.

Figure 26. The mean values of water resistance for the laminate and the coating, for each

type of testing.

Figure 27. The Ret-values of the materials before and after washing.

Figure 28. The mean Ret-values for the laminate and the coating before and after washing.

List of tables

Table 1. Production methods for textile barriers.

Table 2. List of databases and sources of information used for the literature search. Table 3. Specifications of the base weave from Supplier Y.

Table 4. Specifications of the coated and laminated textiles from Supplier Y. Table 5. Impact categories and characterisation methods.

Table 6. List of the test methods used and their specifications. Table 7. Compilation of the studied environmental impacts.

Table 8. Mean values of tear strength for coated textile in warp and weft direction. Table 9. Mean values of tear strength for laminated textile in warp and weft direction. Table 10. The p-values for the tear strength testing in the warp direction, taken from an

ANOVA.

Table 11. The p-values for the tear strength in the weft direction, taken from an ANOVA. Table 12. The p-values for the water column, taken from an ANOVA including all samples

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1. Introduction

“There is no such thing as a bad weather, only the wrong clothes”

Despite being an old saying, this translated Swedish proverb is also expressing a vital part of the history of textile clothing. Wearing clothes as a means of protection against weather and/or body damage has been done for thousands of years (Holmes 2000; Marek & Martinkov

á

2018). Thanks to the right type of clothing, humans are able to walk through burning buildings not being hurt, handle microorganisms and toxic chemicals, and work outdoors under harsh climate conditions while maintaining a normal body temperature.

These types of textile clothing are placed under a category named personal protective equipment (PPE), and are designed for several different applications: construction work clothing, protection against fire, healthcare environments, laboratory work etc. (Marek & Martinkov

á

2018). When it comes to textiles used in physical outdoor activities the materials need to be combined in such a way that the wearer is equipped with a clothing system that – apart from performing the main function as protection – also ventilates and helps to regulate the body temperature (Lomax 2007; Mukhopadhyay & Vinay Kumar 2008). In other words, there are two vital requirements for an outdoor PPE fabric and clothing system:

• Provide protection from weather (and/or other harm)

• Provide comfort by being breathable

Waterproof breathable fabric (WPBF) is the name of a type of textile barrier where the two functions are combined in one textile system. Producing WPBF is a complex challenge. Combining permeability and waterproofness in a garment is creating a material with two main functions that somewhat

contradicts each other (Mukhopadhyay & Vinay Kumar 2008; Hunter & Fan 2009). On the one hand, the textile is supposed to keep the wearer from getting wet. On the other, it should also maintain a comfortable microclimate for the body of the wearer to assure that there is no over- or underheating. This means that when designing a WPBF, there is always a compromise between the two functions (Hunter & Fan 2009).

Using textiles as a means of protection is an important application but protecting the environment from the impacts of the textile industry is equally important. It is widely known that the textile industry has a major environmental impact – both in terms of resource use and pollution

(Naturvårdsverket 2018). Producing WPBF and protective clothing often involves a lot of processing of the materials, to achieve the desired properties. More processing should also imply a larger environmental impact, as the production phase of a garment’s life cycle is where the major environmental impacts – regarding toxicity and climate change – arise (Roos, Sandin, Zamani, & Peters 2015; Naturvårdsverket 2018). Protective clothing is also a product group that is associated with high environmental burden because of the heavy use of toxic chemicals to create, for example, oil-repellent and flame-retardant properties (Schmidt, Watson & Roos 2016).

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considered. Cotton versus polyester is an example of this, where the natural cotton fibre is perceived as superior to the fossil fuel-based polyester. A study from 2014 (van der Velden, Patel & Vogtländer) showed that from a life cycle perspective, cotton actually had higher environmental burden than polyester. This shows that the naturalness of a product might not even be a decisive factor when it comes to environmental impact, and the same might go for other seemingly evident relations.

An environmental aspect that is often overlooked is the location of the production. The textile is often produced in developing countries, for the textile bought in Sweden for example, almost 80% is produced outside the EU. In these textile producing countries limited access to water treatment plants and poor handling of chemicals is common. The energy sources for the production to a larger extent also comes from more unsustainable sources. Coal, which is associated with significant emissions of greenhouse gases, is for example a prevalent source of energy in the largest textile producing country, China (Naturvårdsverket 2018; Huang, Zhao, Geng, Tian & Jiang 2017). This not only contributes to problems in the textile producing countries but could also mean a greater global environmental impact than if the production would have been placed in a region with better equipped production facilities.

Another aspect that adds complexity to the evaluation of a product’s sustainability, is the balance between functionality and environmental burden. A product that is environmentally ‘friendly’

produced might still not be considered sustainable, if the production process too severely compromises the product’s functionality. For example, who would use a sustainably produced raincoat if it could not repel water? When applied to protective clothing, this is of particular importance, as functionality in these garments could be a matter of life and death.

To assess the sustainability of a product therefore requires a model that includes environmental impacts from several different angles.

1.1 Life cycle assessment

Life cycle assessment (LCA) is a method of evaluating the environmental impact of a product or system with a holistic approach that considers the entire process. With LCA it is not possible to push the environmental problems from one part of the life cycle to another, or from one environmental problem to another, since the product or system is evaluated as a whole (Finnveden et al. 2009; Baumann & Tillman 2004). LCA is also a method that takes geography into account, which means that it considers that different regions have different sensitivities to certain environmental impacts and that infrastructure varies between different parts of the world (Baumann & Tillman 2004). These aspects make LCA a suitable method for more comprehensive and fair comparison between different products or systems.

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to incomplete inventory data and characterisation factors1_{for many substances (Baumann & Tillman} 2004; Finnveden et al. 2009). This is especially true when it comes to chemicals used in the textile industry (Roos 2016).

When the raw data has been collected, it needs to be inserted into an LCA software that can calculate the environmental impacts. Ideally, LCA would be a simple method, where data could just be inserted into a software, and all the calculations were made thereafter. However, in reality LCA is a quite complex method. In order to get a result that provides insight into the true environmental impacts, a number of conscious decisions need to be made regarding the choice of inventory data,

characterisation factors and of what processes to include. Making these decisions therefore requires practitioners that have a fundamental understanding of environmental impacts, processes, materials, chemistry etcetera2_.

1.1.1 Impact categories

To make the results of an LCA more comprehensible and relevant, the studied environmental loads are grouped and converted into different impact categories. For many people it is easier to understand the consequences of a term like climate change than of a measurement of greenhouse gases such as CO2, CH4 and N2O. Apart from climate change, examples of common impact categories include

acidification, eutrophication, ozone depletion, toxicity and water use. The choice of impacts to study depends on the type of product or system that is reviewed, as different products or systems are associated with different kinds of environmental problems (Baumann & Tillman 2004).

With regard to the textile industry, a range of impact categories are relevant to mention. Depending on aspects such as type of fibre and dyeing process, there might be different significant environmental loads. Three impact factors that are highly relevant to most textile products are climate change, toxicity and water use3_{. All industrial processes demand the use of energy, and in most cases this} energy does not come from a renewable source. The energy is often derived by burning oil, gas or coal, which causes emissions of carbon dioxide and other harmful substances. The emissions associated with the use and extraction of these energy sources are important contributors to climate change (Fung 2002c; Muthu 2014).

Chemical use and pollution are environmental problems that contribute to toxicity. This impact category can be further divided into ecotoxicity and human toxicity. Ecotoxicity refers to chemical emissions damaging species in the ecosystem, while human toxicity translates to emissions damaging the health of humans (Baumann & Tillman 2004). Damaging the ecosystem and human health is a risk associated with textile products because of the heavy use of chemicals throughout the life cycle. According to a study from 2009 (Olsson, Posner, Roos & Wilson) between 1.5 and 6.9 kg of

chemicals are used per kg of textile during the stages of fibre production, processing, fabrication of the garment and the use phase. A textile process that is related to chemical use is the dyeing process. The

1_{These are indicators that reflect the relative contribution to the environmental impact. The collected} data is multiplied with the corresponding characterisation factor to get a quantitative measure of how much impact the product or service has in different impact categories.

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dye chemicals can be toxic in themselves and can lead to allergies or even cancer, but the wastewater from the dyeing process is also linked to a number of issues. One of these issues is that some dye substances have a high chemical oxygen or biological oxygen demand, which can cause hostile environments to aqueous plants and animals (Kadolph 2013).

The use of water is also important to analyse for textile products. Large amounts of water are being used throughout the life cycle for many textile products. This of course depends on the type of fibre and fabric that is used, since natural fibres like cotton require extensive amounts of water while synthetic fibres only require small quantities. The use of water also depends on what kind of processing the material goes through. Dyeing, sizing and scouring are examples of processes which can be water intensive (Senthil Kumar & Grace Pavithra 2019).

1.1.2 Previous LCA studies on textiles

LCA is a tool that is used more and more for textile products, however there are some common issues associated with LCAs for this specific product category. In a study from 2014, the authors (van der Velden, Patel & Vogtländer) highlighted several problems with LCAs on textiles. One significant problem that they identified was that the data used for the calculation was old and outdated. Data for energy use for different production steps was in some cases taken from the 1990’s, even though significant energy efficiency improvements have been made since then.

Roos brings up another problem with LCAs on textile products, in her doctoral thesis from 2016, which is how toxicity impacts are handled. Even though the use and emissions from chemicals is a major environmental aspect of textile products, toxicity is rarely included as an impact factor in LCAs. This means, according to Roos, that LCAs lack information that could be useful to the textile industry in assessing environmental impact.

1.1.3 The LCA structure

Normally an LCA is used to study the product from cradle to grave – from the raw material extraction to the disposal or recycling of the used product. It is also possible to make LCAs where not all phases of the life cycle are included. An example of this is a cradle-to-gate model, where the product is studied from raw material extraction to finished product at the factory (Baumann & Tillman 2004).

Regardless of the type of LCA that is made, the assessment follows the same structure. This structure consists of the following four main parts (Baumann & Tillman 2004):

1. The goal and scope definition is the first phase, where it is decided what product or system to study and what the functional unit will be. The application of the study, the reason for doing the study and the intended audience should be defined here. The impact categories should also be stated, as well as what processes are being studied, the so-called system boundaries. 2. The life cycle inventory (LCI) is the phase where the data is collected. This usually begins

with a flow model of the system, where the analysed activities are included and their respective inputs and outputs. Calculations are then made in relation to the functional unit. 3. In the life cycle impact assessment (LCIA) phase, the information about inputs and outputs

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4. Interpretations of the findings is the final phase, where conclusions from the LCI and LCIA are made.

A schematic illustration of the phases in the LCA are presented in figure 1.

Figure 1. The four phases of an LCA, as seen in ISO 14040:2006.

1.2 Material testing

An important aspect of environmental sustainability of textiles, is how long they can be used for. In a report from 2016, it was established that doubling the service life of a garment significantly would reduce the carbon footprint and water used, compared to buying a new garment (Roos, Zamani, Sandin, Peters & Svanström 2016). A suitable method for comparing the sustainability of materials is therefore through textile testing, since this could determine how durable the fabric properties are.

1.3 Context

This study is initiated under the project TexBar, a four-year long collaboration between different enterprises and textile researchers from RISE IVF and the Swedish School of Textiles. Through TexBar, the involved parties collaborate to develop new and innovative textile barriers (Mistra 2015). Within the project, the environmental impacts of different textile barriers are also evaluated, including coated and laminated materials.

Laminated and coated fabrics have similar properties and can be used in the same type of products.In a product development phase, it can therefore be difficult to know which material to choose, especially when considering the environmental point of view. Within the group of researchers in the TexBar project, there was a perception that laminates were superior to coatings in terms of environmental performance4_{. However, at this moment, no data or information is found that neither confirms nor} denies that this is the case.

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Workwear is a product category where both coated and laminated textiles commonly are used. One company producing workwear and PPE constitutes the case study for this report, and will hereafter be referred to as Company X. One of their suppliers, referred to as Supplier Y, provides them with barrier fabrics which are used for many of their protective garments.

1.4 Purpose

The aim of this report is to make a comparative analysis of the two textile barriers coating and lamination. The study aspires to clarify which processes during the material production phase that serves as the largest environmental impactor and the type of impact – in terms of climate change, human toxicity and water use – that the different processes accounts for. Furthermore, this study is intended to examine the relation between functionality (mechanical properties and comfort) and the environmental consequences each barrier’s production process amounts to.

1.5 Research questions

1. Are laminates or are coatings responsible for the largest environmental impact based on an LCA?

2. Is it possible to build a model to conclude which one of these barriers that is the most sustainable alternative from a functional and environmental perspective?

1.6 Limitations

This report aims to bring light to the different impacts of coated and laminated textiles in general, but will only study the specific materials from Company X. The study is therefore limited to the raw material, finishes and processes used by their Supplier Y. The finished material will be used in a garment, however this report will only study the material as the fabrication of the garment is assumed to be equivalent regardless of material.

In LCAs a wide range of aspects and impact factors can be studied to get a comprehensive view of the studied product or system. This LCA focus on a cradle-to-gate assessment, where the use and end-of-life phases are not included. Also, a limited number of impact categories will be studied, namely climate change, human toxicity and water use. There are other impacts that could provide relevant information for the analysis, such as ecotoxicity and eutrophication, but they will not be assessed in this report. Within the LCA, the impacts of the handling of the waste will not be calculated for the direct production processes.

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1.7 Ethics

Ethics is an important part of research, and especially when doing a case study. The researchers need to provide correct and specific information, without breaking the rules of confidentiality towards the parties providing them with this information (Vetenskapsrådet 2017). In this report, the businesses constituting the case study wish to be anonymous and are therefore referred to as Company X and Supplier Y. Interviewees from these companies will only be named by their professional title. It is also important to state that the researchers of this study aim to be objective, and do not have any relation with the involved businesses other than that what is stated, nor do they receive any form of

compensation from them.

2. Waterproof breathable fabrics

As stated earlier, textile materials that not only stop water from entering but also let vapour pass through and leave the textile on the outer surface, are called waterproof breathable fabrics (WPBF). True to its name, the main functions required by WPBF are waterproofness and breathability (water vapour permeability).

2.1 Waterproofing ability

When talking about clothing that protects against weather, the term “waterproof” is often one of the first functions that comes to mind. In relation to water repellent fabric which is a function related to the fabric surface energy, surface wetting and water absorption properties (Rehnby 2010; Özek 2018), a waterproof fabric entirely prevents liquid water from penetrating the material. Waterproofness is measured in the amount of hydrostatic pressure (in mm water) that the material can withstand without water penetrating it. For a material to be stated as truly waterproof, a hydrostatic pressure of 5000 mm water (column) is the minimum value (Özek 2018). Garments that are specified as waterproof often have a pressure of 10 000 mm or more stated in their specifications, while PPE or high-quality garments promising complete waterproofness can withstand 15 000 – 30 000 mm water columns (C. Loghin, Ciobanu, Ionesi, E. Loghin & Cristian 2018).

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2.2 Breathability

Being composed of fibres and pockets of air, all fabric are porous materials (Özek 2018) and therefore breathable in various degree. However, the term breathability does not mean that the fabric actually breathes (Holmes 2000). Instead the term is used when describing the function of a material allowing water vapour molecules to move through the material (Özek 2018). This refers to the ability to transmit vapour and thus increase the material’s function as a regulator of body temperature (Mukhopadhyay & Vinay Kumar 2008; Hunter & Fan 2009).

It is through conduction, radiation, convection and evaporation that generated heat can leave the skin and keep a human body at a comfortable temperature (Das, Das, Kothari, Fangueiro & de Araujo 2007; Hunter & Fan 2009). Conduction and radiation are sufficient means of heat loss for a body at rest. When physically active, perspiration that is transferred from the bodies to the surrounding

atmosphere “carries” excess heat away from the skin (Holmes 2000). If water vapour generated by our bodies is prevented from evaporating from the skin – by clothing layers acting as an unbreathable “wall” – condensation is created, resulting an increased humidity and a microclimate which makes the clothes uncomfortable to wear (C. Loghin et al. 2018; Özek 2018). Thus, moisture transmission through a textile fabric plays an important role for comfort, which in turn influence the practical use of the garment. Therefore, understanding the mechanism behind moisture transmission is vital for understanding the performance of WPBF.

When water vapour molecules move through porous materials, for example textiles, it is called water vapour diffusion. This is a result of differences in vapour pressure between material and ambient air (Finch 2017). Moisture is always present in the air in different amounts. The more water molecules present in a certain volume, the higher the vapour pressure. Since pressure difference is a less wanted state than equilibrium, water vapour diffusion occurs from the side of the material which has a higher vapour pressure, to the side which has a lower pressure (Finch 2017). Inside a piece of clothing with perspiration evaporating from a body in movement, the vapour content and thus pressure is higher than on the outside layer of the garment, which results in the vapour diffusion and permeability5_.

To measure permeability, it is common to measure the Moisture Vapour Transmission Rate (MVTR). The MVTR describes the rate moisture can diffuse through one square meter of fabric, from the inner surface to the outer surface, for 24 hours. According to Özek (2018), a rating of 10 000 g/m2_{/day is a} requirement for textiles used in high activity garments. However, when the permeability performance of two or more textile products are to be compared an opposite value is often used, the measure of resistance to water vapour transmission – or in other words resistance to evaporative heat transfer (Ret). Ret is “the water vapour pressure difference between the two faces of a material divided by the resultant evaporative heat per unit area in the direction of the vapour gradient” (ISO 2014) and it gives the permeability of a garment in units of square meter Pascal per Watt, m2_{Pa/W. A lower Ret-value is} an indication of good permeability, where garments with Ret-values under 20 is considered as having “enough” breathability to be worn when being active. More specific, it can be said that:

• 0-6 m2_{Pa/W = very good permeability for high intensity activities,}

• 6–13 m2_{Pa/W = good permeability}

• 13-20 m2_{Pa/W = satisfactory but uncomfortable at intense activities}

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(Özek 2018).

The Ret-value is given by the following formula:

𝑅

_𝑒𝑡

=

(𝑝

𝑚

− 𝑝

𝑎

) × 𝐴

𝐻 − ∆𝐻

_𝑒

− 𝑅

𝑒𝑡0

𝜇

(eq.1) Where:

• pm is the saturation water vapour partial pressure at the surface of the measuring unit (Pa)

• pa is the water vapour partial pressure of the air in the test enclosure (Pa)

• A is the area of the measuring unit (m2₎

• H is the heating power supplied (W)

• He is the correction term for heating power for the measurement of Ret (W)

• Ret0 is the apparatus constant in m2_{Pa/W, for the measurement of Ret (m}2_Pa/W)

(ISO 2014).

Partial vapour pressure, p, is the pressure that a component (here water vapour) exerts independent of all the other components present. It is, according to Raoults law, equal to the vapour pressure of the pure component at that temperature multiplied by the component’s mole fraction in a mixture of components (LibreTexts 2019).

The saturation vapor partial pressure is the vapour pressure when the content of water vapour in the air has reached its maximum amount – any higher and it condenses to liquid phase. As warm air can hold more moisture than cold (LFS 2019), vaporu saturation pressure differs with temperature. At 35°C, close to the temperature at the surface of human skin, the saturation vapour partial pressure is approximately 56 kPa (Engineering Toolbox 2004). So, water vapour pressure is caused by temperature and different amounts of water vapour content in the ambient air.

What is also worth noting is that this definition of breathability is not the same as wicking, which is a fabric property that measures the fabric’s ability to transport moisture away from the body alongside its fibres (Mukhopadhyay & Vinay Kumar 2008; Özek 2018). In order to be specific and not have the two different properties mixed together, it is therefore advisable to do as Holmes (2000) suggests and scientifically refer to breathability as water vapour permeability, which is done in this report.

2.3 Production methods for WPBF

WPBF can be produced by several methods. The main techniques are: • Lamination

• Coating

2.3.1 Lamination

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structure and properties of the components or by adding an adhesive6_{. It is a two-step process in which} the barrier layer is first produced and then laminated to the textile (Fung 2002a). A general

identification factor for a laminate is a clear distinction between the barrier and the textile, where the barrier can consist of film, foil, or membrane (C. Loghin et al. 2018). As for the textile, it can be constructed of either a weave, knit or non-woven (Hunter & Fan 2009).

According to C. Loghin et al. (2018) 90% of the synthetic polymers used for lamination are

polyurethanes. The advantages of this polymer are its elasticity, flexibility, resistance to ageing and natural waterproofness.

Various techniques and machines are available for lamination. The challenge is to preserve the fabric’s original properties at the same time as creating a laminate that is flexible, durable and that lives up to the specified requirements (Mukhopadhyay & Vinay Kumar 2008). Thermoplastic polymers can be directly laminated onto textiles by applying heat and pressure, if the adhesive forces between the components are strong enough7_{(Rehnby 2010). Otherwise an adhesive, in the form of a web, viscous} paste or granulate, is used to combine the two. As a membrane is thin and has poor mechanical strength, it can also be laminated onto a liner fabric for support. This liner fabric is often a lightweight web or knit.

There are four main methods of creating a textile laminate (see figure 2):

1. Lamination to a lightweight web/mesh, placed between the outer fabric and the lining 2. Lamination to the outside of the lining fabric

3. Lamination to the inside of the outer fabric

4. Lamination to both the outer fabric and lining – a three-layer system

In figure 2 the construction of the laminates described above are illustrated.

Figure 2. Schematic illustration of different ways of creating textile laminates.

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2.3.2 Coating

When a polymer is applied as a paste, foam or viscous liquid onto a textile, it is called a coating process (C. Loghin et al 2018). According to Fung (2002a), the definition of a coated textile material is that one or more layers of adherent material has been formed on the textile fabric. Coatings are much thicker than membranes (Holmes 2000) and can typically be identified by the fact that the polymer coating has sunken into the textile surface so that the coating cannot be detached (C. Loghin et al. 2018).

Depending on the type of use, the application method for the coating polymer differs. Direct spreading is the most basic process, by which the polymer is spread directly onto the fabric by using a blade or knife. The type of knife together with the distance between the knife and the fabric surface affects the thickness of the coating and the penetration of the coating paste in the textile8_{. Thereafter the coating} undergoes coagulation and drying to solidify (Holmes 2000). The coating can be done in several application layers depending on use and desired thickness.

Figure 3 illustrates how the cross section differs between a coated and a laminated textile. The coating has sunk into the weave, while the membrane lies on top of the weave. Before the coating is applied, the material is often calendered to make the conditions for getting an even application as good as possible9_.

Figure 3. Schematic illustration of the cross section of a coated fabric (to the left) and a laminated

fabric (to the right).

2.3.3 Techniques for creating a textile coating or laminate

Table 1. List of some production methods for textile barriers.

Method Only lamination Only coating

Wet coagulation Solvent extraction

Melt blown / Hotmelt technology RF/UV/E beam radiation

Mechanical fibrillation Thermocoagulation Solubilizing one component Foam coating

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• Wet coagulation (for micro-porous): A solvent, often dimethylformamide (DMF), is used to make a thermoplastic polymer like PU coagulate to a structure with micropores. The polymer is dissolved in water together with the solvent and then coated onto the fabric or as transfer film. Coagulation of the coating takes place in a chamber with water vapour, where the solvent and polymer are separated, and the polymer separates into a microporous structure. The fabric is then washed and dried to remove the solvent and leave a polymer with an interconnected porous structure.

• Foam coating: Direct coating where the polymer solution is mixed with thickening agent and mixture is whisked with air is blown into it to create a foam. After application and drying the coated fabric is calendared for compression. No solvents are needed in this process. Usually the coating is finished with a water repelling agent.

• Thermocoagulation: Polymer is mixed with two solvents with difference in volatility and coated on the fabric. In a low temperature drying, the solvent with a lower boiling point evaporated and leaves a polymer that has precipitated to a porous structure. A second higher drying process evaporates the solvent that is left10_{. In this process, biological or waterbased} solvent can be used11_.

• Transfer coating: Used when knitted or elastic textiles are to have a thin coating applied. In this process the coating polymer is in liquid phase and spread onto a releasing paper, solidified, then applied with a second layer after which application to the textile is done.

• Solvent extraction: A polymer is dissolved in solvent that mixes with water and is then directly coated. Solvent is extracted in a coagulation bath, after which the coating is dried, cured, and washed.

• Mechanical fibrillation: Only applicable for micro-porous structures. Most known example are the Gore-Tex laminates. A stretching of a polymer film or sheet in both directions creates tiny rips and tears in the structure due to fibrillation and voids formed between fibrils. This leads to a web-like configuration being developed, which gives the polymer its micro porosity.

• Meltblown/hotmelt: Consists of one or more base layer of coarser thermoplastic melt spun filaments and one or more layer of finer thermoplastic microfibers (also met spun) which are bonded by heat. By applying a force (without tearing the fibres), the filaments and microfibers are elongated and straightened respectively in the direction of the force, where the microfibers are packed to form a tight but thin microporous structure.

(Mukhopadhyay & Vinay Kumar 2008; Özek 2018)

10_{Interview with Production Manager at Supplier Y, 2019-05-09.}

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2.4 Hydrophilic and micro-porous structures

There are two main methods for coating or laminating a textile material through which water vapour transmission (WVT) can occur. One is by creating a micro-porous structure, and the other is by using a modified polymer as barrier material, in which intermolecular chemical reactions generates the permeability.

2.4.1 Micro-porous structure

A micro-porous membrane (or coating) consists of an interconnected network of pores within a polymeric structure. The pore size is generally between 0.1-50 μm in diameter (Mukhopadhyay & Vinay Kumar 2008) with a maximum pore size of 2-3 μm at the surface to guarantee waterproofing. The range in pore size makes them large enough for water vapour molecules (40 x 10-6_{μm) to pass} through, but small enough to prevent raindrops (100μm) from entering the membrane, see figure 4. According to Gorji, Bagerzadeh and Fashandi (2017), a membrane is considered as breathable when water vapour at a minimum rate of 400 g/m2_{/day is transmitted through it. The rate of WVT is related} to porosity and thickness, where an increase in WVT is achieved through decreased pore size, while a thicker fabric decreases water vapour permeability (Mukhopadhyay & Vinay Kumar 2008).

The WVT rate (under steady conditions) through a microporous structure with constant porosity and thickness is given by the equation:

𝑊𝑉𝑇 =

𝐴𝐵

𝑇 + 0.71𝑑(1 − 𝐵)

(eq. 2) Where:

• A = a constant

• B = the porosity of the structure (% pore volume)

• T= thickness of the structure

• d= pore diameter (Lomax 1985)

Figure 4. A microporous barrier structure where the porosity allows for vapour molecules to pass through it but prevents penetration from water drops.

Micro-porous materials are thin walled, circa 10 μm (Holmes 2000; Mukhopadhyay & Vinay Kumar 2008), and typically made from polyurethane (PU), polyolefins, polyamides, polyesters, polyether, copolymers or polytetrafluorethylene (PTFE) (Hunter & Fan 2009). As stated previously, the majority

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of these materials consist of PU due to its flexibility and durability (C. Loghin et al. 2018; Mukhopadhyay & Vinay Kumar 2008).

This type of barrier can be made both by coating of the polymer directly onto the fabric surface, or by a two-step lamination process (Mukhopadhyay & Vinay Kumar 2008). Since micro-porous barriers are hydrophobic and oleophilic (having an affinity for oil) there is a risk of oil and grease

contaminating its surface. Everything from body lotions to dirt, salt, detergents and oils can clog the membrane pores and decrease the permeability (Holmes 2000). To prevent this, the barrier is usually layered with hydrophilic PU or treated with a water repellent finish that is non-oleophilic (Hunter & Fan 2009). The most known example of a microporous membrane is probably Gore-Tex (Gorji, Bagerzadeh & Fashandi 2017). This polytetrafluoroethylene (PTFE) structure is said to consist of 1.4 billion pores per square centimetre (Mukhopadhyay & Vinay Kumar 2008).

2.4.2 Hydrophilic structure, non-poromeric

The second kind of method for creating a WPBF, is by using a non-poromeric structure. In this case the migration of water vapour molecules depends on a chemical chain reaction between the molecules and functional groups in the polymer chain (Mukhopadhyay & Vinay Kumar 2008; Hunter & Fan 2009).

The WVT rate through a hydrophilic structure is given by the equation:

𝑊𝑉𝑇 = 𝐷𝑆

(𝑝

1

− 𝑝

2)

𝑙

(eq. 3)

Where:

• D= the diffusion constant, depending on the intermolecular structure of the system, pressure, and humidity.

• S= the solubility coefficient, depending on molecular attraction, pressure and humidity

• (p1-p2) = the partial pressure gradient between the two surfaces of the polymer

• l= thickness of polymer

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Figure 5. Water vapour passing through a hydrophilic polymer.

Sympatex is an example of a hydrophilic waterproof and breathable membrane. It is produced by Akzo Nobel and is made up of polyester (70%) integrated with hydrophilic polyether (30%) and is reported to stretch up to 300% without losing its waterproofness or breathability (Hunter & Fan 2009).

Concerning the type of permeable structure – micro-porous and hydrophilic – there are naturally attributes that are advantaged as well as less advantaged for each type. Solid hydrophilic structures are known to have better tear strength than microporous ones, thanks to their elasticity. Hydrophilic structures are also known to be better barriers against microbial contamination (Fung 2002a). Hydrophilic materials are swelled by water, which could make them heavier than microporous ones. However, thanks to the swelling ability, the hydrophilic structures can not only transport water vapour but also liquid water away from the body, which microporous ones cannot.12

2.5 Water repellent finish for WPBF

As previously mentioned, a water repellent finish can be used to help waterproof a material and protect the microporous structures from oil and dirt. Another important function of this type of finish, is that it can prevent the fabric from getting ‘wetted out’. This is important since a wet fabric could reduce the breathability of a coating or membrane. It should be noted however, that the effectiveness of all water repellent finishes eventually is diminished – due to abrasion, washing or contamination (Fung 2002b).

The most commercially used waterproof formulations, fluorocarbons and siloxanes (silicones), have been shown to have a very negative effect on human health and the environment. Looking at the effects of fluorocarbons, the long-chained molecules have been proven persistent in the environment, bioaccumulative in animals and humans, and toxic in terms of reproduction and development. The short-chained fluorocarbons (fewer than eight carbons) are also environmentally persistent but are thought to be less toxic and less bioaccumulative than the long-chained alternative. There is however little knowledge about the long-term safety of these substances. Siloxanes are less toxic and less persistent than long-chain fluorocarbons, but certain cyclic siloxanes can be very toxic and damage vital organs and fertility (Whittaker & Heine 2018).

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For many PPE, the use of fluorocarbons is the only way to get the type of water repellence that the garment needs to have according to safety standards. According to producers, their customers demand a certain level of durability for their water repellent textiles, while at the same time wanting to use less harmful substances for DWR-finishes. In present day, both suppliers and companies are beginning to develop and evaluating other types of water repellent formulas13_.

2.6 DMF as solvent in coating production

In addition to the use of fluorocarbons and/or siloxanes for water repellence, the production of coatings and laminates involves chemical substances in other processing steps.

The mixing of a coating paste involves several substances with specific functions. Dimethylformamide (DMF) is an organic compound which is used in chemical industry as a solvent, intermediate and additive. With a miscibility with water and most organic solvents, and a high boiling point, it is common as a solvent in the textile industry when processing coatings and synthetic leathers (AFIRM Group 2018).

DMF is derived from formamide, where methyl groups have replaced the hydrogen atoms in the amine (PubChem 2019). Figure 6 shows the chemical composition of DMF.

Figure 6. The dimethylformamide molecule.

When released into the air, DMF can be taken up by humans via inhalation or absorption via skin contact. Classified by REACH (ECHA 2019) as a Substance of Very High Concern (SVHC), DMF is a reproductively toxic substance which can cause skin and eye irritation and cause internal body damage by liver disease (PubChem 2019; AFIRM Group 2018). Through enzymatic oxidation in the liver, the DMF metabolite N-methylformamide (NMF) is formed when DMF is taken up by the body (Wrbitsky & Angerer 1998).

In a study on the exposure to DMF of fabric operatives in a PU production unit, a statistical comparison of air sample of DMF with levels of NMF in the urine of the workers was made. The results of the study suggested that, 95% of the total body burden due to DMF exposure is explained by inhalation (Osunyanya, Adejoro & King 2001). Therefore, the need for high capacity ventilation and monitoring of indoor emissions is very important to ensure a nontoxic workplace. Furthermore, several authors (Wrbitzky & Angerer 1998; Osunsanya, Adejoro & King 2001) highlight the importance of PPE to limit dermal absorption of DMF, or exposure to it.

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2.7 New techniques within textile barriers

Research on the environmental impacts in relation to production of waterproof and permeable textile barriers is continuously being done. During recent years, small producers as well as widely known ones (such as Gore-Tex and Sympatex), struggle with how to provide effectiveness and durability without exposing the environment and humans to potential toxic harm (Shenh, Zhang, Xu, Yu & Ding 2016).

2.7.1 Fabrics bases on Biomimetics

The mimic of biological mechanisms is called biomimetics and is basically a copying of functions from nature. These mechanisms have been used to develop fabrics which imitates characteristics in natural systems. One biomimetic technique is the so-called lotus effect. Here, a structure is created that mimics the structure of a lotus leaf. The mechanism relies on the plant’s hydrophobic cuticle, or protective skin. On a microscale, the cuticle has tiny bumps with wax on their tops covering its surface. This gives a surface that is rough, wax-like and has a low surface tension. Dirt and

contaminants are prevented from sticking to it and are instead washed of by water droplets falling on the leaves (Kapsali 2018).

According to Kapsali (2018), biomimetics in textile application has a lot of potential but is somewhat of an unexplored field. Future research in the field of nature designs can hopefully lead to the

development of more advanced and sustainable textiles.

2.7.2 Electrospun nanoweb membranes

Electrospinning is a technique that can be used to manufacture micro- and nanoscale fibres of polymers with properties related to mechanical, thermal, optical and electrical performance that exceeds the performance of conventional fibres (Asmatulu & S. Khan 2019; X. Gu, Li, Luo, Xia, H. Gu & Xiong 2018).

In comparison with conventional production of porous membranes – such as hot melt or mechanical fibrillation – electrospinning offers a less costly way of producing membranes. Their high porosity and small fibre diameter contribute to a high breathability. The limitation with electrospun

nanomembranes is the difficulty in regulating the pore size, which in turn gives a good permeability but a poor water resistance (X. Gu et al. 2018). That the nanofibrous mats are not homogenic in their structure affects their strength and abrasion resistance negatively (Knížek, Karhánková, Bajzík & Jirsák 2019). This causes problems when applying the nanomembrane in the textiles industry (X. Gu et al 2018). However, just as with membranes from “normally” sized fibres the nanofiber mats can be laminated onto a liner (support fabric) to reduce some of its frailness (Knížek et al. 2019).

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is used. It is also free of fluorocarbons, thus making a less harmful impact on the environment than its competitors (Nanomembrane 2019).

3. Research methods and materials

To answer the research question number one, an LCA was done through a case study of a the laminated and a coated textile. As explained in section 1.1, the execution of an LCA is a time consuming and extensive work. This pertains not only to the collection and organisation of raw data, but also to the knowledge of how to transform the data into measurable units of environmental impact and calculating a result that is both legitimate and comprehensible (see 1.1).

To answer research question number two, a model was first designed to evaluate the sustainability of the two barriers. This evaluation model was based on the combination of two parameters: the

functional performance and the environmental performance of each barrier. Figure 7 shows a schematic illustration how the evaluation model was designed.

Figure 7. A basic outline for the design of the evaluation model.

3.1 Methodological framework of the evaluation model

The first step in building the evaluation model was to outline the methodological framework, which is presented in figure 8. Since the idea behind the model was to evaluate both the functional and

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Figure 8. The methodological framework within the evaluation model.

The flow to the left represents the method of material testing for functional performance, while the right flow represents the method of LCA for environmental performance. Each step in the two methods is connected to one or more of the four sources of information. These sources are illustrated in the middle column of the figure; Interviews, Literature study, Discussions with experts within the area, and Visit at production site. These information sources are accounted for in section 3.3.

3.2 The report structure

The report structure was just as the evaluation model divided into two main methods: determining the functional performance by textile testing and determining the environmental performance by LCA.

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Figure 9. Schematic diagram over the report design.

As figure 9 shows, the report is based on a case study. A case study was done because there is an endless number of ways to make coated and laminated textiles. It would have been difficult to outline the processes for the LCA and to make any conclusions about the materials if the study was to

compare all coated and laminated fabrics. It would also have been too extensive to study all aspects of coated and laminated processes. A more detailed comparison of two specific fabrics was therefore thought to be more interesting than a general one.

Company X was chosen to be the case for this project because they use state-of-the-art coated fabrics. Their supplier has the ability to produce both coated and laminated materials, which makes it easier to do a comparison, since the weave and finishing are the same for both textiles. The disadvantage of using a specific case is of course that it is more difficult to draw any general conclusions about the two types of materials, and it is impossible to know if other coated or laminated textiles would behave in the same way or have the same environmental impact.

3.3 Sources of information

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3.3.1 Interviews

Interviews were held in person at visits at the office of Company X and at the production site of Supplier Y. The structure of the interviews has not followed a general form of question-answering, but rather one of a conversation. These interviews provided information and insight used for identifying and choosing important functions for testing, environmental factors and process parameters. In the report the interviewees have been referred to by their professional title, as both Company X and Supplier Y wished to be anonymous.

3.3.2 Literature search

To find information about previous research on the topic, the project was initiated with a literature search. This search for literature then continued throughout the project. The primary way of searching was through databases. This was done with search phrases mainly related to LCA, coating and

lamination. Examples of commonly used databases, search phrases and filters are presented in table 2.

To find information about LCA the book The Hitch Hiker’s guide to LCA (2004) by Baumann and Tillman was the primary source used. For information about coating and lamination different types of sources were used – both books and articles – with the main one being the article A review on

designing the waterproof breathable fabrics part I: Fundamental principles and designing aspects of breathable fabrics (2008) by Mukhopadhyay and Vinay Kumar.

Some of the sources used for coating and lamination processes may be classified as old. The risk of referring to techniques that are out-of-date was minimised by using new publications as support to the major source mentioned above. Also, interviews and the visit at the production site suggested that the techniques mentioned in the older literature still are relevant.

Table 2. List of databases and sources of information used for the literature searching. Examples of

search phrases are shown in the second column, and examples of filters for limiting the searches in the third column.

Most used databases Search phrases (examples) Filters (examples)

Primo Scopus Google Scholar

Journal of Industrial textiles

“membrane”

“coating” “waterproof” “textile” “membrane” AND “waterproof” AND “permeab*

“nanoporous” AND “membrane*” AND “clothing”

“LCA” OR “Life Cycle Assessment" AND "textile" AND waterproof AND coating

environment* AND coat* AND textil*

Peer Reviewed Year of publication: 2015-2019 Areas: - textiles - permeability - waterproofness - polyurethanes - laminated fabrics - polymers - coated fabrics - water vapour

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3.3.3 Discussions with experts within the area

For the execution of the study, a fundamental understanding of LCA was necessary. This meant that discussions with LCA experts were necessary, since the authors had limited prior knowledge. As explained in 1.1, an experienced LCA practitioner is needed for choosing databases, impact categories and instructing the use of the software. The authors rely on the knowledge in LCA of Dr Roos for this aspect.

3.3.4 Visit at production sites

For the collection of raw data and information, a visit to the European production site of Supplier Y was made. The visit included a step-by step walkthrough for every production process of the two barriers, discussions with the Sales Manager and Production Manager, and collection of raw data for each processing step.

3.4 Material

The materials investigated in this project are a laminated and a coated fabric, and the weave that creates the base for both barriers. The end use of the textiles is in workwear garments produced by Company X, and all three materials are supplied by their Supplier (Y). From Supplier Y, the specified properties of the materials were given. A selection of these properties is shown in tables 3 and 4.

Table 3. Specifications of the base weave from Supplier Y.

Material Weight Number of end (warp) Number of picks (weft)

Base weave 124 g/m² 60 yarns/cm 32 yarns/cm

Table 4. Specifications of the coated and laminated textiles from Supplier Y.

Material Membrane/ coating Weight Tear strength (ISO 13937-2: 2000) Water- column (ISO 811:2018) Watercolumn (ISO 811:2018), after washing 5x60°C + drying Water vapour resistance (ISO 11092:2014) Laminated fabric Microporous PU 150 g/m² Warp: 20 N Weft: 40 N 1000 cm 700 cm 9 m2_Pa/W Coated fabric Hydrophilic PU 165 g/m² Warp: 22 N Weft: 55 N 1000 cm 500 cm 12 m2_Pa/W

The coated fabric is used in workwear by Company X, while the laminate is a product under development. The reason for choosing these specific barriers is that they have the same base weave, which was an important part in making a fair comparison between the different barriers. The raw data collected for the LCA is taken from a production batch of 1200 m for the coated textile and a

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3.5 LCA: Goal and scope

The first phases of the LCA are the goal and scope definition and the inventory analysis.

Since information about many parts of the goal and scope has been stated earlier in this report, it will not be repeated here. Within this goal and scope, the functional unit, impact categories,

characterisation factors and data specifications are presented.

3.5.1. Functional unit

LCA is a relative approach where the environmental impact relates to the function of a product or product system (Baumann & Tillmann 2004). The function is expressed as a quantitative unit by which the comparison between different products or product systems is made possible. In this study the definition of the functional unit was one square meter (1m²) of finished fabric.

3.5.2 Impact categories studied

In this study, the assessments are made according to the impact categories climate change, human toxicity and water use. These impact categories have been selected in dialogue with supervisor Dr Sandra Roos and modified considering the goal and the time frame. In addition to this, the amount of chemicals used in each process was calculated, as well as the direct water use during the production of each barrier.

The impact score, IS, is the measured score that each impact category adds up to. It is calculated according to the following formula:

𝑆 = ∑

𝑖

∑ 𝐶𝐹

𝑥,𝑖

× 𝑀

𝑥,𝑖 𝑥 (eq. 4) Where:

IS = impact score for impact category, for example human toxicity CFx,i= characterisation of substance x released to compartment i

Mx,i= the emission of x to i

(Huijbregts et al. 2010)

In table 5 the four impact categories and their characterisation method and measuring unit is shown. Each characterisation method and unit are explained in the following three sections.

Table 5. Impact categories and characterisation methods.

Impact category Characterisation method

Unit Reference for characterisation method Climate change Global warming potential kg CO2

equivalent

CML IA Water use Water scarcity potential m3_/m2_month _AWARE Human toxicity

non-carcinogenic

Human toxicity potential of DMF in indoor air

disease cases/kg emissions

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3.5.2.1 Climate change

Global warming potential (GWP) is a way of comparing the impacts on climate change from emissions of different gases over a period of 100 years. The emissions of greenhouse gases are calculated as a relative factor of kilograms of a carbon dioxide equivalent. As CO2 is used as a reference, the GWP of CO2 is 1, and all other emitted gases contributing to climate change are put in relation to CO2; the higher the GWP of a gas, the more it warms the earth during a 100-year period (EPA 2017). For example, using the CO2 equivalent factor for methane found in CML IA database, it has a factor of 30 for a period of 100 years. In that period, emission of 1 kg methane therefore has a 30 times larger impact on climate change than what 1 kg CO2 has.

3.5.2.2 Water use

For calculation of the water use in this study, the method AWARE is used. The AWARE method “is based on the quantification of the relative available water after the demand of humans and aquatic ecosystems has been met, answering the question: What is the potential to deprive another user (human or ecosystem) when consuming water in this area?” (Boulay et al. 2017, p.369). The CFaware is a quantitative factor ranging between 0.1 to 100, and can be used to weigh water use in an LCA to evaluate its potential impact on both humans and ecosystem. Hence, this potential impact of water use is equivalent to a water scarcity footprint. For complete calculation of CFaware see appendix 1.

For calculation of the CFaware, the inverse of the difference between availability and demand per area per month is used to quantify the potential of water deprivation (eq. 5). This value of available water remaining per surface area in a given watershed, is put in relation to the world average after demands of humans and ecosystem have been met. In cases of a negative AMDi, when the demand is greater than the availability, the CF is set to a maximum value of 100. When AMDi is less than 1% of the world average available water remaining (AMDworlds avg), the CF is set to the minimum value of 0.1.

𝐶𝐹

_{𝐴𝑊𝐴𝑅𝐸}

=

𝐴𝑀𝐷

𝑤𝑜𝑟𝑙𝑑 𝑎𝑣𝑔

𝐴𝑀𝐷

_𝑖 (eq. 5) Where:

AMDi= water Availability Minus Demand in m3/m2 month

AMDworld av= 0.0136 m

3_/m2_{month = consumption weight average of the AMD}

i over the whole world

(Boulay et al. 2017)

Environmental impact of textile barriers